The present invention relates to a tool chuck, especially for holding various tool bits, for example twist drill bits, so as to be driven by a machine tool, in particular a portable drill press. The machine tool may include a percussion feature and the tool bit may thus be additionally subjected to impact forces. The chuck to which the invention relates includes a core or mandrel on which moves a hollow collar with interior conical surfaces against which glide at least two chucking jaws. The chuck further includes an elastic member tending to urge the mandrel or core away from the surrounding collar. A chuck of this general type is known, for example from U.S. Pat. No. 3,737,170, Warner et al., (to which the German Disclosure Document DE-OS No. 1,957,289 corresponds), assigned to the assignee of this application. The chuck described there is to be used with impact drills for holding a tool bit securely against impact and oscillatory stresses which at the same time permitting a relatively easy release of the drill bit without the application of high forces.
A further known tool chuck is described in the German Disclosure Document No. 23 47 364 for use in impact or percussion drill service. It is a disadvantage of the known tool chucks that the elastic member which urges the mandrel and the chuck jaws apart is disposed immediately adjacent to the chuck jaws and is thus exposed to the effects of the impacts that the chuck jaws themselves are subjected to during the use of the tool.